United States
Department of
Agriculture
Forest
Service
Region 5
Forest Service
Plumas National Forest
39696 Hwy 70
Quincy CA 95971
Feb. 13, 2008
Authors - Colin Dillingham, Kyle Merriam, Michelle Coppoletta, Chris Christofferson
Date:
Penstemon personatus Monitoring
PURPOSE
The primary objective of Penstemon personatus monitoring within the HFQLG project area is to
assess the effect of forest management activities, including timber harvest operations, chainsaw
thinning, hand piling, oak enhancement, and broadcast and pile burning on species presence and
abundance. Prior monitoring efforts have included photo points and frequency plots. In 2006, we
began establishing permanent monitoring plots to measure P. personatus cover both before and
after different treatments being implemented across the HFQLG project area.
OBJECTIVES
Management Objective: To maintain P. personatus frequency or percent cover of at least half
of the pre-treatment mean, and to evaluate the significance of declines in P. personatus cover
relative to untreated controls.
Sampling Objective: To detect a 50% change in the frequency or percent cover of P.
personatus with a 90% confidence that our estimated mean is within 10% of the true value.
Management Response: If sampling detects a decline of greater than 50% in P. personatus
cover or frequency after treatment, the treatment would be considered detrimental to P.
personatus occurrences and would not be advised. We will also evaluate the significance of
declines in P. personatus cover in comparison to untreated control plots.
METHODS
A number of different monitoring methods have been used to evaluate the response of P.
personatus to HFQLG project implementation. These include cover estimates using 1 m2
quadrats and line intercept methods, as well as frequency estimates (species presence or
absence). These three methods are described in more detail below.
Cover estimates using 1m2 quadrats: In 2005, Feather River Ranger District botanists
installed seven 1m2 plots to monitor the effects of a prescribed burn on P. personatus. The plots
were installed approximately one week prior to the prescribed fire and were dispersed over 1.5
miles along a ridge top. Each plot was marked with rebar and percent cover of all vascular plant
taxa was estimated to the nearest 1%. The number of P. personatus flowering stems were also
counted. Plots were reread in the summer of 2007.
Frequency: Frequency monitoring of P. personatus has been conducted at a number of sites
across the Plumas National Forest, following methodology described in the Quincy Ranger
District Monitoring Strategy (1990). For the purpose of HFQLG monitoring, frequency
monitoring has only been conducted at a single site on the Mt. Hough District, the Waters 29
Caring for the Land and Serving People
Printed on Recycled Paper
Unit. Frequency plots were established at this site on Sept 6, 2001 by Colin Dillingham and John
Dittes. The 300 ft transect contained 60 milacre (6 ft 6 inch square) plots. Plots were placed at
50-ft intervals within the P. personatus population. At each plot it was determined whether P.
personatus was present or absent. A GPS file was created in the summer of 2005 and is filed
with the Penstemon monitoring data on the server (K:/tm02/botany/monitoring info/Penstemon
personatus/).
Cover estimates using line intercept: In 2006, botanists across the HFQLG project area began
establishing permanent transects within P. personatus populations to estimate changes in cover
using line intercept methods as described in Elzinga et al. (1998). The intent was to establish
consistent monitoring protocols for this species so that data might be pooled across sites. So far
line intercept monitoring has been conducted at 11 sites, including 3 control units, 4 group select
units, 3 mechanical thin units, and one hand thin unit (Table 1). Our goal is to monitor at least 3
sites supporting P. personatus for each treatment type, including untreated controls. In 2008, our
priority will be to establish additional plots in hand thin and prescribed burn units, and to
complete post-treatment monitoring at the 6 sites where treatments were implemented during the
fall of 2007.
Table 1. Permanent monitoring units established as of 2007 for P. personatus using line intercept methods.
Unit Name
Ararat1031-a
Faggs Control
Oak EnhancementControl
Ararat1031-b
Ararat1045
Guard 442
Guard 845
Waters 29e
Guard 15
Guard 16H
Oak EnhancementTreat
# of
Transects
6
6
5
Ranger District
Feather River
Feather River
Almanor
Treatment
Planned
Control
Control
Control
6
6
6
6
6
Feather River
Feather River
Mt. Hough
Mt. Hough
Mt. Hough
Group Select
Group Select
Group Select
Group Select
Hand Thin
8
6
5
Mt. Hough
Mt. Hough
Almanor
Mechanical Thin
Mechanical Thin
Mechanical Thin
Date Treatment
Implemented
8/15/2007
7/24/2007
10/14/2006
8/5/2007
8/15/2007
Monitoring
Completed
Pre-treatment
Pre-treatment
Pre-treatment
Pre-treatment
Pre-treatment
Pre-treatment
Pre-treatment.
Pre- and posttreatment
Pre-treatment
Pre-treatment
Pre-treatment
At each site, between five and eight 200-ft parallel transects were established along a randomly
located baseline. Parallel transects were located 50 ft apart. Pilot sampling conducted in 2006 at
the Waters 29 Unit indicated that 6 transects would be sufficient to detect a 50% change in the
mean cover of P. personatus within a 90% confidence interval. Along each transect, P.
personatus cover is measured using line intercept methods. In addition, at 20-ft intervals
overstory canopy cover is recorded using a moosehorn densitometer, and duff and litter depth are
measured. All data is maintained in the QLG effectiveness monitoring database
(K:/tm02/botany/monitoring/QLG monitoring/monitoring effectiveness database/).
RESULTS
2
1. Cover estimates using 1m2 quadrats
MANAGEMENT OBJECTIVE
Cover estimates used to evaluted the effect of prescribed burning on the Feather River Ranger
District in 2005 found no statistical difference in percent cover of P. personatus after the
prescribed burn (paired t-test, df=6, P=0.16) (Figure 1). However, the lower 90% confidence
interval in the post treatment plots was below 50% of the estimated pre-treatment mean. A paired
t-test also indicated that there was a significant decline in the number of P. personatus flowering
stems after the prescribed burn (df=6, P=0.01) (Figure 2).
Figure 1. Changes in P. personatus cover after a prescribed burn. Our target management threshold of half the pretreatment value is indicated by the red line.
Percent
P. personatus Cover
14
12
10
8
6
4
2
0
Pre
Post
Pre- or Post Treatment
Figure 2. Changes in in P. personatus flowering after a prescribed burn. Our target management threshold of half
the pre-treatment value is indicated by the red line
P. personatus flowering stems
Number of Stems
70
60
50
40
30
20
10
0
Pre-treatment
Post-treatment
SAMPLING OBJECTIVE
3
Our sampling objective was to estimate the post treatment mean with a 90% confidence that we
were within 10% of the estimated true value. The mean cover for P. personatus after the
prescribed burn was 5.3%. The 90% confidence interval was 4.4%, or 83% of the estimated
mean. Therefore we did not meet our sampling objective for percent cover. The mean number of
P. personatus flowering stems was 0.143 after the prescribed burn. The 90% confidence interval
was 0.27, or 188% of the estimated mean, so our sampling objective for flowering stems was not
met.
MANAGEMENT RESPONSE
Based on these data it appears that prescribed burning may be detrimental to P. personatus
flowering. However, further monitoring of this population and comparisons with prescribed burn
treatments at other sites might help determine if decreased flowering has long term consequences
for the presence and abundance of P. personatus at this site, and if this result is consistent across
sites. This prescribed burn completely consumed the duff layer, and burned with relatively high
severity. It is possible that less severe burns would have different effects on P. personatus.
Although we did not find a significant decline in P. personatus percent cover, we did observe a
decrease of more than 50% of the pre-treatment value. Given that our sampling objective was not
met, we may want to increase the number of plots established at the site before we conclude that
prescribed burning is detrimental to this species.
2. Frequency estimates
MANAGEMENT OBJECTIVE
The estimated frequency of P. personatus in the Waters 29 Unit following hand-thinning
treatments was 56.7% (± 18.6 %; Table 2). The estimate of change between 2006 and 2007 was
a decrease of 6.7 % frequency. Based on a paired t-test, this change was not statistically
significant (P=0.18, SE: 0.07), which suggests that hand-thinning had little effect on the number
of plots occupied by P. personatus in the Waters 29 Unit.
Table 2. P. personatus frequency plot data
Pre-treatment
2006
Year
2001
% Frequency
Standard Error
90% confidence interval
61.6
Not calculated
Not calculated
63.3
0.062
± 16.2
Post-hand thin
2007
56.7
0.063
± 18.6
SAMPLING OBJECTIVE
The 60 frequency plots were not adequate to meet our sampling objective, which was to be 90%
confident (P value of 0.1) that frequency estimates were within 10% of the estimated true value.
The estimated frequency for 2007 was 56.7 % (Table 2), which would make our target
confidence interval in absolute units 5.67 % (or 10 % of 56.7). The calculated confidence
interval in 2007 was ± 18.6 % (or 33 % of 56.7); therefore we did not meet our sampling
objective.
MANAGEMENT RESPONSE
4
We found that the number of plots which contained P. personatus did not change significantly
after hand thinning. This suggests that the spatial arrangement of P. personatus did not change
(plots where the species was found prior to the treatment also had the species after the
treatment). However, frequency is not a measure of the cover, vigor, or abundance of P.
personatus at the site.
Even though the 90% confidence interval was greater than our target of 10%, the range of values
(38.1 to 75.3 % based on the 90% CI) is above our target management threshold of 31 % (see
Figure 3). Therefore, no management response is required at this time. However, future
monitoring efforts may want to establish additional plots in order to meet our stated sampling
objective at this site.
Figure 3. Change in P. personatus frequency after hand thinning. Error bars denote the 90% confidence interval.
The target threshold of 31% is shown in red.
85
75
65
55
45
35
25
Target Threshold = 31 %
2006 (pre-treatment)
2007 (post-hand thin)
Monitoring Year
3. Cover estimates using line intercept methods
Forest Wide Trends in Cover
Line intercept transects established to measure P. personatus cover at 12 different sites across
the HFQLG project area found that P. personatus cover was significantly different across sites
and varied from 0.7% at the Oak Control site to almost 20% at Mt. Ararat site (Figure 4).
Figure 4. Mean cover of P. personatus across 12 sites where line intercept transects have been established.
5
0.4
COVER
0.3
0.2
0.1
0.0
-a -b 45 ro 15 5a 6h 42 45 lC in 9e
31 31 t10 ont rd d1 d1 d4 d8 tro nTh rs2
t10 at10 rara s C Gua uar uar uar uar Con Thi ate
a
G G G G ak ak W
ar ar A agg
Ar Ar
F
O O
PROJECT
A linear regression model found that P. personatus cover was not significantly related to either
overstory canopy cover or duff depth (df = 2, 68, R2=0.061, P=0.64).
MANAGEMENT OBJECTIVE
Effect of Hand thinning: As described in the frequency monitoring section above, the Waters 29
Unit was hand thinned in 2006. The effect of hand thinning on P. personatus cover at the Waters
29 Unit was also measured using line intercept methods, and values were evaluated in
comparison to a control plot. Both sites were measured before and after the hand thinning
treatment (Table 3).
Table 3. P. personatus line intercept data, including species cover, overstory canopy cover, and duff depth. The
90% CI is included in parentheses.
Year
2006- Hand
thin Unit
Pre-treatment
2006 Control
unit
Pre-treatment
2007-Hand thin
unit
Post-Treatment
2007-Control
unit
Post-Treatment
Mean % cover (PEPE)
Mean % overstory
cover
Mean duff and litter
depth (cm)
4.03 (±1.83)
83.3 (±0.11)
2.9 (±1.87)
57.6 (±6.1)
4.15 (±2.35)
69.2 (±7.6)
4.40 (±1.46)
53.0 (±10.0)
5.02 (±2.27)
2.80 (±0.55)
8.32 (±1.83)
5.54 (±1.41)
The estimated change in P. personatus cover between 2006 and 2007 was a very small increase
of 0.12 % at the Waters 29 Unit after hand thinning, and an increase of 1.5% at the control site
(Figure 5). A two-way Analysis of Variance (ANOVA) found that these changes in cover were
not statistically significant (df=1,20, P=0.94).
Figure 5. Change in P. personatus cover after hand thinning at the Waters 29 Unit in comparison to the control site.
Error bars indicate the calculated 90% confidence intervals. The 50% target threshold is shown with a red line.
6
5
4.5
4
3.5
% Cover
3
2006
2007
2.5
2
1.5
1
0.5
0
Control
Waters
Site Name
Sampling Objective:
The 6 transects established at the Waters 29 Unit were not adequate to meet our sampling
objective, which was to be 90% confident that we could detect a 50% decline in P. personatus
cover within 10% of the true value. The mean post treatment P. personatus cover was 4.4%, and
the calculated 90% confidence interval was ± 2.7%, or 61% of the estimated mean. Therefore we
did not meet our sampling objective. A power analysis showed that the 6 transects established at
this site could only detect a 100% change in the cover of P. personatus within the 90%
confidence interval, while 24 transects would be necessary to meet our stated sampling objective.
Management Response:
Although first year post treatment data suggests that hand thinning does not negatively affect P.
personatus, failure to meet our sampling objective indicates we may not be able to reliably detect
a 50% decline in P. personatus cover at this site. Replication of this treatment type and the
inclusion of additional transects may be necessary to conclusively evaluate the effects of this
treatment on P. personatus.
DISCUSSION SUMMARY AND RECOMMENDATIONS
MANAGEMENT OBJECTIVE: We have only evaluated the effects of two treatments in this
preliminary analysis. A prescribed burn conducted at a single site on the Feather River District in
2005 decreased P. personatus cover and significantly decreased the number of P. personatus
flowering stems. Although the decrease in cover was not statistically significant, the lower end of
the 90% confidence interval was less than 50% of the pre-treatment mean.
A hand thinning treatment at the Waters 29 Unit was evaluated with both frequency and line
intercept plots. There was no statistically significant change in frequency or cover after the hand
thinning treatment, and percent cover actually increased slightly.
7
Recommendations: We suggest reevaluating the management objectives, particularly at sites
where pre-treatment means are very low. For example, we would probably not consider a 50%
decline in cover that is only 0.5% to be a biologically significant change.
Sampling Objective: This preliminary analysis demonstrates that our initial sampling designs,
including both frequency and cover estimates, have failed to meet our sampling objectives. The
calculated confidence interval has ranged from 33 to 188% of the estimated mean, much greater
than our target of 10%.
Recommendations: Replication of treatment types, and pooling of sites in the statistical analysis,
may increase our statistical power in future analysis. However, other steps might be taken to
improve our sampling design, including:
Consider collecting frequency data at all sites. Frequency monitoring at the Waters 29
Unit had the least variation (90% confidence interval was 33% of estimated mean).
Frequency estimates may minimize observer error (Elzinga et al. 1998). Collecting
frequency data with a management objective of avoiding 50% declines in species
presence may also be more biologically meaningful than preventing very small declines
in species cover.
Establish additional transects. A sample size analysis of the Waters 29 Unit indicates that
24 transects would be necessary to detect a 50% change in P. personatus cover within a
90% confidence interval. The necessary number of transects will vary at each site, and
further sample size analysis can be conducted after two years of data are available at each
site.
Revise our sampling objective to increase the minimum detectable change. For example,
6 transects are adequate to detect a 100% change at the Waters 29 Unit.
Revise our sampling objective to decrease the Type I and Type II error rates. For
example, 12 transects are adequate to detect a 50% change at the Waters 29 Unit within
an 80% confidence interval.
Management Response:
Based on these preliminary data it appears that prescribed burning may be detrimental to P.
personatus flowering, and that hand thinning may not have a deterimental effect on this species
presence or cover. However, failure to meet our sampling objectives suggests these results may
be an artifact of low statistical power.
Recommendations: We have a large number of sites where post treatment data has yet to be
collected. After we have completed data collection at all of these sites we will likely have a
better idea of the effects of these treatments on P. personatus. Combining data from multiple
sites will also probably improve our statistical power to detect changes. However, by taking steps
to improve our sampling design and better meet our sampling objectives, we can increase our
certainty that measured changes in P. personatus presence and/or cover are accurate and any
management response is well justified. Therefore, we recommend collecting data at the rest of
the sites, and using more plots to meet our sampling objectives, before recommending any
specific management response.
LITERATURE CITED
8
Quincy Ranger District (Anonymous). 1990. 1990 Penstemon personatus Monitoring Summary
for the Quincy Ranger District. Unpublished on file at the Mt Hough Ranger District,
Penstemon Personatus Monitoring Files. 6pp.
Elzinga, C., D. Salzer, and J. Willoughby. 1998. Measuring and monitoring plant populations.
Bureau of Land Management, Denver, Colorado, USA, 492 Pages.
9